Plasmonic TiO2:Au composite layers deposited in situ by chemical spray pyrolysis

• TiO2:Au composite layers were deposited in situ by chemical spray pyrolysis.
• Au-nanoparticles with a size of 8–20 nm are embedded in the TiO2 matrix.
• The size of Au-nanoparticles is controlled by the deposition temperature.
• [Au] concentration in the spray sol has minor effect on the Au-nanoparticles size.
• Plasmon resonance effect in TiO2:Au composite layers was tuned from 570 to 620 nm.

Composite TiO2 layers with embedded Au-nanoparticles with a size of 8–20 nm were deposited in situ by chemical spray pyrolysis. EDS studies show that increase in the deposition temperature from 260 to 300 °C decreases the [Au]/[Ti] ratio down to the vanishing of Au at in 400 °C. The mean crystallite size of the Au-nanoparticles is slightly decreasing from 17–21 nm to 10–13 nm with increasing deposition temperature from 260 to 300 °C. However, the annealing at 400 °C has minor affect on the size of the Au-nanoparticles. Annealing at 400 °C results in crystalline anatase TiO2 matrix with its mean crystallite size decreasing with increasing the [Au]/[Ti] ratio in the composite layers. The total transmittance and reflectance spectra of the TiO2 and TiO2:Au composite layers are complemented by the Mie calculations, showing that the red shift of the surface plasmon resonance band from 570 to 620 nm is associated with the increase in the refractive index of the TiO2 matrix.